1. Field of the Invention
This invention generally relates to an apparatus for feeding documents, such as original documents, through a reading section for reading an image on a document, and, in particular, to a document feeding apparatus particularly suitable for use in facsimile machines, copying machines and the like.
2. Description of the Prior Art
An automatic document feeding apparatus is used in various office machines, and, in particular, in facsimile machines. A typical prior art document feeding apparatus incorporated in a facsimile machine is illustrated in FIG. 2. As shown, the document feeding apparatus includes a pick-up roller 1, a separating roller 2 and a feed roller 3, which together define a document feeding section for feeding original documents 4 one by one. An electromagnetic clutch 5 is mounted on a shaft of the feed roller 3 and a document sensor 6 is provided for sensing the presence or absence of documents. A pair of guide plates 7 and 8 is provided for defining a transportation path for transporting an original document through a reading section. Thus, the original documents 4 are transported along this transportation path one by one when fed.
Transportation rollers 9 and 10 are provided spaced apart from each other along the document transportation path. The roller 9 is located at the entrance to a reading section for reading an image of each of the original documents 4 and the roller 10 is located at the exit of such a reading section. Pressure rollers 11 and 12 are also provided to be in pressure contact with the respective rollers 9 and 10. A drive motor 13 is also provided and its power is transmitted to a follower pulley 14 through an endless belt 15. The follower pulley 14 is also operatively associated with the rollers 9 and 10 through an endless belt 16, so that the power transmitted from the drive motor 13 through the endless belt 15 is in turn transmitted to each of the rollers 9 and 10 through the endless belt 16.
A contact glass 17 is disposed in the reading section of the document feeding apparatus, and each of the original documents 4 moves in contact with the contact glass 17 when transported through the reading section, whereby the image on each of the original documents 4 is optically read, typically by a scanning method. A document detector 18 is also provided between the roller 9 and the contact glass 17 and a stamper 19 for providing a stamped mark on each of the original documents 4 to indicate the fact that original documents have been optically read.
The operation of the above-described document feeding apparatus will now be described with reference to a timing chart shown in FIG. 4.
(1) In the first place, when a start key (not shown) is depressed by the operator while original documents 4 have been detected to be set by the sensor 6, the drive motor 13 is activated and the clutch 5 is energized so that the pick-up roller 1 and the feed roller 3 start to rotate and at the same time the bottom-most sheet of original document 4 is separated from the stack of original documents 4 by the separating roller 2 and fed.
(2) When the leading edge of the original document 4 thus fed is detected by the sensor 18 after it has moved past the roller 9, the clutch 5 is deenergized so that the feed roller 3 is set in a freely rotatable state, thereby serving as a follower roller. When the leading edge of the original document 4 has reached the reading position, the drive motor 13 is temporarily deactivated and thus the entire drive system is brought to a halt to thereby set a stand-by condition.
(3) Upon receipt of a confirmation signal from another station through a pretransmission protocol, the drive motor 13 is again activated and a reading operation of the original document 4 is initiated.
(4) As the original document 4 is transported through the reading section and when its trailing edge is detected by the sensor 18, the clutch 5 is again energized so that the next following original document 4 begins to be fed.
(5) When the trailing edge of the first original document 4 has reached a stamp position after moving past the sensor 18, the drive motor 13 is deactivated so that the entire drive system is brought to a halt. And, then, upon completion of receiving a receipt confirmation signal from the other station (approximately 300 milliseconds) and stamping the original document thus read (approximately 300 milliseconds), the drive motor 13 is again set in motion to have the first original document 4 discharged out of the document feeding apparatus. During this time period, the rollers 9 and 10 follow the operation of the drive motor 13.
(6) Then, it returns to step 2.
As may be understood from the above description, since the rollers 9 and 10 follow the operation of the drive motor 13, while the preceding document is temporarily halted because of a transmission completion protocol procedure and a stamping operation, the drive motor 13 must be deactivated. As a result, the feeding operation of the next following document 4 must also be temporarily halted.